White Grubs

family: scarabaeidae
species: phyllophaga errans
common names: (p. fusca) june, ten-lined (polyphylla crinita) may, or dung beetles, chafers; white grubs
hosts: most vegetables, carrots, corn, potatoes, rutabagas, tomatoes
notes: Small to large, robust elongate-oval, dull to brilliantly colored. Antennae short lamellate. Nocturnal. Larvae white, grub-like C-shaped adults destructive to foliage and larvae serious root pests of many crops.

THE FOLLOWING (UNTIL OTHERWISE NOTED) IS FROM: GERBER, H.S. 1983.
MAJOR INSECT AND ALLIED PESTS OF VEGETABLES IN BRITISH COLUMBIA.
MINISTRY OF AGRICULTURE AND FOOD.

White Grubs

• Ten-lined June beetle, Polyphylla crinita LeConte
• June beetle, Phyllophaga errans (LeConte)
• June beetle, Phyllophaga fusca (Froelich)

They occur in all vegetable-growing areas in British Columbia. Heaviest populations occur in cultivated crops following the breaking of long-established sod plantings. White grubs are the larvae of June beetles.

Vegetables Attacked:

Most vegetables, carrot, corn, potato, rutabaga, tomato

Injury:

In the spring, white grubs cut off seedlings and transplants beneath the soil surface at the main stem or root. Later in the growing season they feed on roots, tubers and bulbs. Feeding damage is most severe during the second and third years of larval development. White grubs are a particularly serious pest of potatoes where they chew deep, round-bottomed holes up to 12 mm in diameter.

Insect:

There are three species of white grubs in British Columbia. The ten-lined June beetle is the most common species in the coastal areas. It is 25 cm long, mottled grey-brown, with longitudinal white stripes and prominent antennae. Beetles of the most common species in the Interior are 2 cm long and a shiny dark brown. Beetles fly and frequently are attracted to bright lights. They are called June beetles because of their prevalence in that month. White grubs or larvae of both species are thick-bodied, white with dark rear end, brown head and legs. Larvae are 3 mm long when hatched, 1 cm by the first fall, 2.5 cm by the second fall and 3 cm when mature. Typically, they are found in a curled position with legs facing inward.

Life History:

White grubs require about three years to develop; grubs and adults overwinter. Adults lay eggs in the soil within 7 cm of the surface. Larvae hatch after two or three weeks and feed until fall when they migrate down in the soil to more favorable temperature ranges. In the spring of the second year, larvae return to near the surface to continue feeding and in the fall they again go deep into the soil. In the spring of the third year, larvae return to feed near the surface and mature by mid-season. They pupate in earthen cells 6 to 8 inches below the surface. Beetles develop in two to three weeks; most remain in the soil until late May or early June of the following year, when mating and egg-laying occur.

Control:

Control practices are preventive and must be undertaken before seeding or transplanting. Apply recommended insecticides and incorporate into the soil to depths of at least 15 cm. Fumigants may also be used, but are only effective if the temperature at the soil surface is over 10C. Shallow ploughing and frequent cultivation in early summer will reduce populations of white grubs in infested land by exposing them to birds, skunks and other predators.